The present invention is directed to a method and apparatus for modeling characteristics of a vehicle occupant during a vehicle crash event and using that model in the control of an actuatable restraint including compensating for monotonicity of misuse conditions.
Crash sensing algorithms for use in actuatable occupant restraint systems to discriminate between deployment and non-deployment crash events are known in is the art. These algorithms are adapted to discriminate between particular types of crash events for particular vehicle platforms. Such algorithms not only control whether the restraint is actuated, but the timing of the actuation.
One known type of actuatable occupant restraint system includes an air bag. An air bag restraint system includes an electrically actuatable igniter, referred to as a squib. Such systems further include a crash sensing device for monitoring for a vehicle crash event. When a deployment crash event is determined to be occurring from the monitored crash event using an appropriate crash algorithm, an electric current of sufficient magnitude and duration is passed through the squib to ignite the squib. The squib, when ignited, ignites a combustible gas generating composition and/or pierces a container of pressurized gas, which results in inflation of the air bag.
Many known crash sensing devices include an electrical transducer or accelerometer for sensing a vehicle crash event. The accelerometer provides an electrical signal having an electrical characteristic indicative of the vehicle""s crash acceleration. An evaluation circuit, such as a microcomputer, is connected to the output of the accelerometer. The microcomputer determines one or more crash metrics from the crash acceleration signal such as crash acceleration, crash energy, crash velocity, crash displacement, and/or crash jerk. Crash metrics provide crash metric values which are measures of crash intensity. The microcomputer then performs a crash algorithm using the determined crash metrics to discriminate between a deployment and non-deployment crash event. When a deployment crash event is determined to be occurring, the restraint is actuated, e.g., the air bag is deployed.
One difficulty in discriminating between Ddeployment and non-deployment crash events is, of course, the proper evaluation of no-fire (non-deployment) crash events that have a relatively low crash severty, e.g., a 6 MPH (10 KPH), zero degree barrier crash. Another difficulty encountered in crash discrimination is the processing of signals resulting from, what is referred to herein as, vehicle xe2x80x9cmisuse events.xe2x80x9d These misuse events include the vehicle being subject to rough road conditions, potholes, curb strikes, etc. Such misuse events result in the crash sensor, e.g., accelerometer, outputting signals to the microcomputer. The microcomputer processes these signals resulting from the misuse events which could result in crash metric values. It has been found that misuse events have monotonicity in certain crash metrics in that an increase in the severity of the misuse event results in determined higher crash metric values. It is desirable to (i) not only prevent deployment of the restraint as a result of a misuse event, but (ii) quickly reset the metric values back to a zero state at the end of the misuse event.
The present invention is directed to a method and apparatus for modeling a vehicle occupant including hastening the resetting of crash metrics to compensate for monotonicity of misuse events.
In accordance with the present invention, a spring mass model is provided for use in an actuatable occupant restraint system. The model comprises a switchable spring constant having a value responsive to a determined virtual crash velocity value.
In accordance with another aspect of the present invention, an actuatable occupant restraint system is provided comprising a crash sensor mountable to a vehicle and providing a crash signal in response to a vehicle crash event, crash velocity determining means for determining a crash velocity value from a crash signal, and crash determining means for determining the occurrence of a vehicle crash event in response to the determined crash velocity value. The crash determining means includes a spring mass model for use in the crash determination. The spring mass model includes a switchable spring constant switchable to a value responsive to the determined virtual crash velocity value. In accordance with another embodiment, the apparatus further includes crash displacement determining means responsive to the crash signal for determining a virtual crash displacement value. The switchable spring constant is further responsive to the determined crash displacement value.
In accordance with another aspect of the present invention, an actuatable restraint system comprises an accelerometer mounted to the vehicle for providing an electric signal indicative of crash acceleration. A spring mass model is coupled to the crash acceleration signal for providing a modified crash acceleration signal indicative of the virtual acceleration of a vehicle occupant. Crash velocity determining means determines a virtual crash velocity value from the virtual crash acceleration signal. Crash displacement determining means for determining a virtual crash displacement value from the virtual crash acceleration signal. Crash determining means monitors the virtual crash velocity value and the virtual crash displacement value and determines the occurrence of a crash event in response thereto. A predetermined crash velocity value and a predetermined crash displacement value define a first quadrant switch boundary. First determining means determines when the value of virtual crash velocity value and the virtual crash displacement value is within said first quadrant switch boundary. A predetermined crash velocity value and a predetermined crash displacement value define second quadrant switch boundary. Second determining means determines when the value of the virtual crash velocity value and the virtual crash displacement value is within said second quadrant switch boundary. Means are provided for controlling the spring value in response to the value of the virtual crash velocity value and the virtual crash displacement value being within the first and second quadrant switch boundaries.
In accordance with another aspect of the present invention, a method is provided for using a spring mass model in an actuatable occupant restraint system. The method comprises the steps of switching a spring constant value in response to a determined occupant crash velocity value.
In accordance with another aspect of the present invention, a method is provided for controlling an actuatable occupant restraint system comprising the steps of mounting a crash sensor to a vehicle and providing a crash signal in response to a vehicle crash event, determining a crash velocity value from the crash signal, and determining the occurrence of a vehicle crash event in response to the determined crash velocity value. The step of determining the occurrence of a vehicle crash event includes using a spring mass model and selecting a spring constant value responsive to the determined crash velocity value. In accordance with another aspect, the method further includes the steps of determining a crash displacement value, and wherein the step of selecting a spring constant value is further responsive to the determined crash displacement value.